Methods of fabricating environmental barrier coatings for silicon based substrates

Abstract

A method of protecting an article from a high temperature environment, the method includes providing a substrate comprising silicon, forming a slurry coating composition, wherein the composition comprises a metallic silicon powder, a rare-earth oxide, an alkaline earth metal oxide, an aluminum oxide, or a combination comprising at least one of the foregoing, and a binder effective to chemically stabilize the slurry coating, applying a layer of the slurry coating over the substrate, and heat-treating the slurry coating under conditions sufficient to oxidize the metallic silicon powder and form an alkaline earth metal aluminosilicate, a rare-earth silicate, an aluminum silicate, or a combination comprising at least one of the foregoing bonded to the substrate.

1 . A method of protecting an article from a high temperature environment, the method comprising:
 providing a substrate comprising silicon;   forming a slurry coating composition, wherein the composition comprises:   a metallic silicon powder;   a rare-earth oxide, an alkaline earth metal oxide, an aluminum oxide, or a combination comprising at least one of the foregoing; and   a binder effective to chemically stabilize the slurry coating;   applying a layer of the slurry coating over the substrate; and   heat-treating the slurry coating under conditions sufficient to oxidize the metallic silicon powder and form an alkaline earth metal aluminosilicate, a rare-earth silicate, an aluminum silicate, or a combination comprising at least one of the foregoing bonded to the substrate.   
     
     
         2 . The method of  claim 1 , wherein applying the layer further comprises spraying, slip-casting, brush-painting, dipping, pouring, rolling, spin coating, or a combination comprising at least one of the foregoing techniques. 
     
     
         3 . The method of  claim 1 , wherein the binder comprises a colloidal silica present at a level in a range of about 1% by weight to about 20% by weight, based on silica solids as a percentage of the entire slurry composition. 
     
     
         4 . The method of  claim 1 , wherein the slurry coating composition further comprises an organic stabilizer comprising an alkane diol, a glycerol, a pentaerythritol, a fat, a carbohydrate, or a combination comprising at least one of the foregoing. 
     
     
         5 . The method of  claim 1 , further comprising cleaning the substrate prior to applying the slurry coating composition. 
     
     
         6 . The method of  claim 1 , wherein the heat treatment is carried out an oxygen-bearing atmosphere at a temperature of about 1000 degrees Celsius to about 1600 degrees Celsius. 
     
     
         7 . The method of  claim 1 , wherein the metallic silicon powder comprises a plurality of silicon particles. 
     
     
         8 . The method of  claim 7 , wherein the particles are spherical, hollow, porous, rod-like, plate-like, flakes, fibrous, or a combination comprising at least one of the foregoing. 
     
     
         9 . The method of  claim 1 , wherein the alkaline earth metal aluminosilicate comprises barium, strontium, barium-strontium aluminosilicate, or a combination comprising at least one of the foregoing. 
     
     
         10 . The method of  claim 1 , wherein the rare-earth silicate comprises a monosilicate of yttrium, ytterbium, lutetium, erbium, dysprosium, a disilicate of yttrium, ytterbium, lutetium, erbium, dysprosium, or a combination comprising at least one of the foregoing. 
     
     
         11 . The method of  claim 1 , wherein the aluminum silicate comprises mullite, mullite-barium strontium aluminosilicate, mullite-yttrium silicate, mullite-calcium aluminosilicate, or a combination comprising at least one of the foregoing. 
     
     
         12 . The method of  claim 1 , wherein the slurry coating layer undergoes less than about 5% shrinkage during the heat treatment. 
     
     
         13 . A method of fabricating an environmental barrier coating on a substrate, the method comprising:
 providing the substrate, wherein the substrate comprises silicon;   forming a water based slurry coating composition, wherein the composition comprises:   a metallic silicon powder;   a rare-earth oxide, an alkaline earth metal oxide, an aluminum oxide, or a combination comprising at least one of the foregoing; and   a binder effective to chemically stabilize the slurry coating;   disposing a bond layer over the substrate, wherein the bond layer comprises a silicon metal;   disposing a layer of the slurry coating over the bond layer; and   heat-treating the slurry coating under conditions sufficient to oxidize the metallic silicon powder and form an alkaline earth metal aluminosilicate, a rare-earth silicate, an aluminum silicate, or a combination comprising at least one of the foregoing bonded to the substrate.   
     
     
         14 . The method of  claim 13 , further comprising cleaning the substrate prior to disposing the coating layer and/or bond layer. 
     
     
         15 . The method of  claim 13 , wherein the bond layer has a thickness of about 2 to about 6 mils. 
     
     
         16 . The method of  claim 13 , disposing the slurry coating layer further comprises spraying, slip-casting, brush-painting, dipping, pouring, rolling, spin coating, or a combination comprising at least one of the foregoing techniques. 
     
     
         17 . The method of  claim 13 , wherein the metallic silicon powder comprises a plurality of silicon particles, wherein the particles are spherical, hollow, porous, rod-like, plate-like, flakes, fibrous, or a combination comprising at least one of the foregoing. 
     
     
         18 . The method of  claim 13 , wherein the slurry coating layer undergoes less than about 5% shrinkage during the heat treatment. 
     
     
         19 . The method of  claim 13 , wherein the substrate is a turbine engine component. 
     
     
         20 . A method of fabricating an environmental barrier coating on a substrate, the method comprising:
 providing the substrate, wherein the substrate comprises silicon;   forming a water based slurry coating composition, wherein the composition comprises:   a metallic silicon powder;   a rare-earth oxide, an alkaline earth metal oxide, an aluminum oxide, or a combination comprising at least one of the foregoing; and   a binder effective to chemically stabilize the slurry coating;   pre-oxidizing the substrate to form a bond layer;   applying a layer of the slurry coating over the bond layer; and   heat-treating the slurry coating under conditions sufficient to oxidize the metallic silicon powder and form an alkaline earth metal aluminosilicate, a rare-earth silicate, an aluminum silicate, or a combination comprising at least one of the foregoing bonded to the substrate.